Electric power distribution panelboards and switchboards are currently available which accept circuit breakers and electric switches by means of a plug-on connection to the bus bars arranged therein. U.S. Pat. No. 4,744,003 describes one such panelboard arrangement. When electric switches or circuit breakers are to be installed on-site within such an operating panelboard or switchboard, the electric power must be temporarily discontinued and the panelboard or switchboard disassembled before such electric switch or circuit breaker can be installed. Since the switchboard and panelboard equipment accept the same-sized circuit breakers and electric switches, the "electrical enclosure" as used herein includes both panelboard and switchboard enclosures. Where modifications must be made to the electrical enclosure interior in order to install the electric switches or circuit breakers, some time is required before the power can be turned ON. This disruption in electric power within an industrial environment could cause scheduling problems both with respect to the related equipment as well as to operating personnel.
U.S. patent application Ser. No. 388,452, filed Aug. 2, 1989, entitled "Electric Power Distribution Panelboard-Switchboard Assembly", describes one such assembly which can accept circuit breakers and electric switches by means of a modular enclosure without requiring that the electrical enclosure be electrically de-energized.
With some electrical enclosures, it is often convenient to plug the electric switch or circuit breaker directly onto the edge-mounted electric bus bars with minor modification in which case the electrical enclosure must be de-energized to prevent damage to the equipment as well as to personnel. To deter electrical circuit with the bus bars in the event that the electrical enclosure becomes inadvertently energized, some means should be employed to prevent direct access at all times to those bus bars that are not connected with the modules, electric switches or circuit breakers.
U.S. Pat. No. 4,754,247, entitled "Molded Case Circuit Breaker Accessory Enclosure", describes a circuit breaker having an electronic trip unit and accessory devices mounted within the circuit breaker cover. The accessory devices are accessed by means of an accessory cover without affecting the integrity of the circuit breaker case which contains the circuit breaker operating components such as the operating mechanism, contacts and arc chute. A wire conductor access slot formed within the circuit breaker case allows for the egress of the wire conductors leading to the accessories while an arc vent slot formed within the circuit breaker case adjacent the arc chute provides supplemental gas venting to the arc gases that are generated during intense circuit interruption. When such side-vented circuit breakers are used within electrical enclosures containing edge-mounted bus bars, the bus bars should be shielded from direct contact with the arc gas by-products that accompany the arc gas evolution from the arc vent slots.
U.S. patent application Ser. No. 627,147 filed Dec. 13, 1990 entitled "Electric Power Distribution Panelboard-Switchboard Bus Bar Insulation Shield" describes a plastic or fiber insulation shield that is arranged over the energized bus bars. However, field modification must be made to the insulation shield to allow for flush-mounting of the shield to the electric switch-circuit breaker modules when the electric switch and circuit breakers are of increased size.
Accordingly, one purpose of this invention is to provide convenient and inexpensive adjustable bus bar insulation shields that can be installed either at the factory or on-site.